One of the challenges of modern cellular communication systems is the quality of the coverage at a cell edge. Wireless transmit receive units (WTRUs) located at a cell edge may experience a high amount of interference from both a base station (BS) and the WTRUs in adjacent cells. As a result of this interference, the typical average throughput measured at a cell edge may be significantly lower than the average throughput in areas close to the cell center.
To address this problem, recent research efforts have focused on cooperative communications. One way to improve the throughput at cell edge, and also extend the coverage, is to use relays. In some deployment scenarios, namely the coverage holes, the WTRU cannot receive the BS transmission. Relays configured either as repeaters or used in a simple 2-hop mode may be used to provide coverage extension. The benefit of relays extends much farther than addressing the coverage extension. When used in a cooperative fashion, relays may provide throughput enhancement for the WRTUs located at the cell edge. Various schemes for cooperation between the BS and the relay for the downlink, or between the WTRU and the relay for the uplink, have been studied in the literature. This invention defines ways to partition the information transmitted by the BS and the relay to enable IR/Chase combining based cooperation in the context of a HARQ framework.
Preliminary performance evaluation of multicast cooperation schemes assumes the use of rateless coding. However, since the framework of existing Long Term Evolution (LTE) and WiMax systems do not readily allow for the implementation of rateless coding, it would be desirable to have a method and apparatus to partition the information bits transmitted by both the RS and the BS to the WTRU during Phase 2 of the communication in order to employ hybrid automatic retransmission request/incremental redundancy (HARQ/IR) methods to approach the performance attained using rateless codes.